Owner: VSAT for Marine URL:http://autotrack-vsat.blogspot.com Join Date: Thu, 31 May 2007 03:46:38 -0500 Rating:0 Site Description: Autotrack VSAT technology that used for Marine, Maritim, Ship and Associate Site statistics:Click here
Below Decks Equipment 2007-05-28 20:36:00 Antenna Control Unit (ACU) & Terminal Mounting Strip (TMS) consists of :Antenna controller names.Displays ACU and PCU software version number on power up. Provides operator interface to control the antenna through the Pedestal Control Unit (PCU).Interfaces to Ship’s Gyro Compass for heading information (heading relative to True North). Interfaces to GPS for ships location information (Latitude & Longitude).Anttena Controller Names consists of :Antenna Control Unit (ACU)Tracking Antenna Controller (TAC-92)Digital Antenna Controller (DAC-97)Pedestal Control Unit (PCU) consists of :Optional connection to a personal computer allows remote control of ACU & antenna when using PCDAC software.Controls tracking (Step Track or Conscan) of the antenna through the PCU.Controls pointing and targeting through the PCU. Antenna Controller ConnectionsRear panel connections are as follows :AC Power - Module includes AC input Receptacle (110/220 cable), ON/OFF Switch and removable Voltage Select/F Read more:Below
, Equipment
Antenna ConScan 2007-05-27 21:12:00 Antenna ConScan section consists of :ConScan (Conical Scanning) - Uses a bore-sight shift of the signal entry into the throat of the OMT. Provides 75-150 RPM sampling of signal level on the four quadrants of the dish to provide intelligent tracking. Provides Timing marks of boresight location relative to the four quadrants of the dish (up, down, left & right).Conscan controller.Feed Modifications on ConScan :Ku-Band Feed - Eccentric scalar plate, motor drive and timing mark sensor. C-Band Feed - Eccentric throat, motor drive and timing mark sensor.Dual Band Feed. - Eccentric C-Band throat, Ku-Band teflon wedge, motor drive and timing mark sensor.The ConScan controller function is for :Timing Marks from feed (dish quadrant location of the feed eccentricity).AGC from IF signal.Compares Timing marks to AGC in near real time.Timing Marks from feed (dish quadrant location of the feed eccentricity) AGC from IF signal.Compares Timing marks to AGC in near real time. Read more:Antenna
Feed Strut Assembly 2007-05-27 20:42:00 Feed Assembly
consists of :Scalar Plate - Improves the gain of the feed, recovering stray receive energy and focusing of transmit energy to improve illumination of the dish surface.OMT (Orthogonal Mode Transition) - Transition from an Orthogonal Mode chamber to standard Waveguide flanges appropriate for the frequency of usage. Must be designed specifically for the frequency of operation, must be the same f/D ratio as the dish, and polarization mode (Linear and/or Circular). Polarization Angle (PolAng) motor(s).Waveguide Filters.LNAs, LNBs, and LNCs - LNAs, LNBs and LNCs - Low Noise Amplifiers, Low Noise Block (down) Converters and Low Noise Converters.Polarization Angle (PolAng) motor(S) consists of :5VDC Pulse - Very light duty servo motor. Shaft rotation position dependant on duty cycle (ON state time Vs OFF state time) of a 5VDC pulse. This normally drives a small dipole inside the feed to adjust polarity or to set the mode (linear or circular) of the feed.24VDC - Polarity of th Read more:Strut
Antenna Reflector 2007-05-25 01:45:00 The Gain & Efficiency of the dish is directly related to:Size of reflector (in square centimeters).Type of reflecting surface.Parabolic curve accuracy.Focal type of the reflector.Struts.Type of reflecting surface consists of Mesh and Solid. Mesh is Framed sections of screen material form a light weight reflector, but is not as efficient as solid surface dishes and has higher level side-lobes.The solid type of reflecting surface consists of :Spun - Least efficient of the solid dishes because the surface is not smooth and the ridges cause some energy to be lost as stray reflections.Hydro-formed - Good surface accuracy, efficiency and low side-lobes.Precision - Very high surface accuracy, efficiency and low side-lobes .Parabolic curve accuracy is how accurately formed the reflector surface curvature is determines how accurately the energy captured by the dish is focused to the focal point.Focal type of the reflector consists of :Direct Focus - Feed and Scalar block receive signal from t Read more:Antenna
Above Decks Equipment 2007-05-23 21:34:00 TVRO Above Decks Equipment
(ADE)Component Identification :The Radome Assembly : Provides for the mechanical mounting and environmental protection of the antenna assembly.Base frame, legs and braces - This assembly provides a rigid attachment to the ship by being bolted, or welded, to the deck of the ship. Radome panels and Radome Cap - When properly bolted together and sealed with silicon sealant, this assembly provides an environmental enclosure for the antenna. This protects the antenna from rain and salt water and also prevents wind from disturbing the pointing of the antenna. A GPS Engine may be fitted to the radome cap, or any other suitable location nearby.The Support Assembly : Mechanical support for the antenna. Rigidly attached to the ship via the Base Frame, therefore, provides the antenna a mechanical reference to the bow-line of the ship.Support stand - Appropriate stand height to facilitate full range of motion of the dish (size) mounted on the equipment frame.Support pos
Basic Satellite Information 2007-05-23 01:49:00 Satellite OrbitsClarke orbit 22,753.2 miles up, directly over the equator (0.0 Latitude).Satellites in Clarke orbit revolve around the earth at the same speed, appearing to be stationary when viewed from earth(Satellites’ orbital velocity matches the Earth's rotational velocity).Commonly referred to as Geostationary or Geosynchronous.Commonly referred to by their longitudinal position (000-180 East & West or 000-360 East) because they stay in position at their assigned longitude.About 170 currently in Geostationary Orbit relaying Telephone, Data and Television signals.Geosynchronous Orbital Spacing is controlled by agreements with multi-national regulatory organizations, to prevent interference by multiple satellites providing the same services.Polar orbiting satellites travel north/south and circle the earth every 90 minutes. Typically weather, GPS, and spy satellites.Transponders - Majority of today's satellites have :At least 24 transponders per BandWide-band transponders capab Read more:Basic
, Satellite
Autotrack VSAT Antenna Introduction 2007-05-22 00:55:00 The antenna will be used onboard a ship and it will have to be able to provide uninterrupted satellite usage while under a variety of motion - we are a leading manufacturer of Marine Stabilized Antenna
Pedestals.What are the key points :Pointing/Targeting - Accurately driving the antenna to a precise Azimuth and Elevation angles in three dimensional free space to be consistent with where the satellite signal is emanating from. Stabilization - Maintaining the Azimuth and Elevation pointing angles while the ship is rolling, pitching and turning.Tracking - Use of the received satellite signal level to continuously evaluate and optimize the pointing angles of the antenna for maximum signal level reception.Definitions of other relevant terms :Relative (REL)Mechanical azimuth rotational position of the antenna relative to the Bow of the ship. When the antenna is pointed inline with the Bow of the ship the REL display should be 360.0/000.0. Range of display is 000.0-359.9.Azimuth (AZ)True A Read more:Introduction
Pointing the VSAT Antenna 2007-05-22 00:31:00 Pointing the VSAT Antenna
– Beam vs Mechanical Axis as used for Physical, or Course Elevation Adjustment :Pointing the VSAT Antenna – Setting the Antenna Course Elevation Adjustment : Read more:Pointing
Basic VSAT 2007-05-21 23:00:00 Finding the required "look angle" has become very easy with the advent of the Internet and the World Wide Web.The following WWW Locations are just examples of the many sites possible:Our primary resource for satellite look angle calculations is Loral SkyNet’s SST calculator. It can be found and downloaded from their website: http://www.skynet.com/tech_resources/tools/tool_us.aspZip CodeLatitude/LongitudeAccounts for Antenna offset values in calculationsPolarization always calculated as ‘horizontal’ downlink (+/- 90 degrees if “vertical” downlink)"Online Satellite Calculations" at http://www.home.online.no/~jensts/satellite.html (Nokia) Domestic and International Perspective using:Lat/Long onlyAdditional Satellite/Engineering Calculations Read more:Basic
Link Budget 2007-05-21 22:47:00 - The process of correctly sizing uplink and downlink paths- Takes into account:Established Satellite performancePath Loss (22,300 miles traversing space)Atmospheric effects (weather, ion storms, sunspots, etc.)Frequency bands used (Ku, C, Ka)Hub uplink antenna and amplifier performanceDownlink antenna size and receiver noise figureLink Budget Rain :Design for the specified availability99.5% availability will give you about two days of outage per year99.9% will give just 8 hours of outage per yearNote that only the Uplink at the Hub can compensate for rain, by using the UPC
Modulation 2007-05-21 22:29:00 Inbound Vs Outbound Transmission Characteristics :Outbound- Continuous output, bandwidth shared among remote sites receiving TDM frames- Emphasis on inexpensive receiver/LNB- High bit rate (up to 32Mbps)Inbound- Random access, transmitter bursts as required to communicate with the hub- Emphasis on inexpensive modulator- Medium bit rate (up to 2Mbps, with large scale VSAT)
Basic Satellite Communications 2007-05-21 21:14:00 Deciding On SatelliteCommunications
?There are the advantages of Satellite Communications :Geographical Coverage UnsurpassedMinimal ‘line-of-site’ difficultiesExtremely reliable (99.9% Up time)Extremely Reliable Data Broadcast or MulticastSingle Vendor TypicallyEasy Remote Site DeploymentSupports multiple applications:Streaming Video and Audio applicationsData applicationsVoice applications; Voice Over IPWhy Satellite Communications Added Advantages?1. Ideally suited for point-to-multipoint and large distributed networks2. Capable of asymmetrical bandwidth3. A single point of management allows for easier traffic analysis/management4. Operational Low Bit Error Rate (BER); typically >10-85. Capable of simultaneous delivery of data to an unlimited number of remotes6. Independence from typical telephone infrastructure7. Private Network capabilitiesCommunications link :Satellite Component consists of :- Transponders- power Read more:Basic
Pedestal Control Unit 2007-06-06 02:35:00 The Pedestal Control
Unit (PCU) uses inputs from the level cage sensors to calculate the amount of torque required in each axis to keep the antenna pointed within +/- 0.1 degrees of the desired position target. The basic control loops for Cross-Level, Level and Azimuth are shown in the control Loop Diagram. The primary sensor for each loop is a gyroscopic rate sensor mounted in the level Cage Assembly. This sensor reports all motion of the antenna to the PCU. The PCU immedietly responds by applying a torque in the opposite direction to a disturbance or command input to bring the antenna to its desired position. Both the instantaneous output of the rate sensor (Velocity Error) and the integrated output of the rate sensor (Position Error) are used to archieve the high pointing accuracy specification.The calculated torque commands are converted to a 5 Volt differential analog signal by a Digital to Analog converter (D/A) and sent to each of three Brushless Servo Amplifiers. These amplifie
Antenna Pointing/Stabilization/Tracking 2007-06-06 02:24:00 There are 4 primary componenet in antenna section where they make it stable in tracking the satellite signal :1. Antenna
Control Unit - Master, controls the antenna through the PCUInterface with Ships Gyro CompassInterface for GPS inputInterface with computer to Monitor and Control the ACUControls Pointing
and Targeting of the antennaControls Tracking
2. Pedestal Control Unit (PCU)Reads sensorsControls MotorsControls Stabilization
of the antennaTakes pointing and tracking direction from the ACU3. ACU-PCU Control Signals - Pedestal M&CACU RS422 input/output via the Base MUXPCU RS422 input/output via the Pedestal MUXBase and Pedestal MUXes are mirror tuned4. Software versionsAre matched to hardware and functional capabilitiesACU and PCU software versions are reported by the ACU
Serial port connections 2007-06-06 02:07:00 Monitor and Control ConnectionsThe monitor and Control port allows external control from a modem, ASCII terminal or PC. SeaTel supplies a windows based antenna control program called PCDAC with allows choosing satellites and tracking functions and dialog box control of tracking and searching functions.The DAC-97 is wired as a DTE device for direct connection to a modem. For connection to another DTE device such as a terminal or PC, a null modem cable is required . connect the null modem cable between J11 on the back of DAC-97 and the ASCII terminal or PC serial interface port. Set the terminal or PC to 4800 baud, 8 bits, no parity (9600 baud operation is available on the Aux serial Board only by installing a jumper at D1). Enable the interface by selecting the system TYPE parameter under the MODE/SETUP display and verify that 8 or a combination that includes 8 is selected.The DAC-97 is available with one or two NMEA/M&C ports installed at J13 and J11. if two ports are installed , use Read more:Serial
, connections
System Block Diagram 2007-06-05 00:54:00 System Block Diagram
consists of three section as describe below :TVRO System Block Diagram.TXRX System Block Diagram.Other inputs to the system.TVRO System Block Diagram consists of :Antenna Control Unit (ACU)Base MUX - Ped MUX (M&C and IF *DC*)Signal path to/from feedTVRO Equipment (TVRO Systems)TVRO Equipment (TVRO Systems) consists of :Multiplex switch or splittersSatellite receiversModulatorsStandards ConvertersCombiner/AmplifierOther distribution equipmentTXRX System Block Diagram consists of :Antenna Control Unit (ACU)Base MUX - Ped MUX (M&C and IF *DC*)Signal path to/from feedTX/RX Equipment (TX/RX Systems ONLY)TX/RX Equipment (TX/RX Systems ONLY) consists of :Satellite ModemIF SplitterRadio M&C Terminal (or PCDAC)MultiplexerOther Distribution equipmentOther inputs to the system consists of :Ships Gyro CompassGPSPCDACRadio M&CUnlimited Azimuth System Interconnect ADE - BDEPedestal Power Supply Read more:System
Other Inputs to the System 2007-06-05 00:39:00 There are two other inputs to the system :Global Positioning System
(GPS) : NMEA signal - ASCII text DATA in RS-422 differential data signaling standard. Input is connected to an Aux Serial Port Adapter on the rear of the DAC-97. Updates the Latitude & Longitude of the ACU about once per second.PC Computer (PCDAC) :Remote Monitor & ControlTestsDiagnostic strip-chartBelow is ficture of NMEA signal :
Nmeah Gyro Information 2007-06-05 00:31:00 When the ACU is configured for gyro type 2, there are two heading displays. The display on the left shows the remote PCU heading register and the display on the right shows the local heading register. In software version prior to 3.24, the right hand display always shows 0000 since this register reading the SBS heading input and there is no data being supplied on this input. The left hand display will show any changes in the NMEA heading updates immediately as they are passed on from the NMEA interface board to the ACU processor and subsequently up to the remote PCU processor. It is recommended that the ACU be set to GYRO TYPE 2 for confirming that the NMEA interface is functioning properly by observing the left hand display and verifying that it changes in sync with the gyrocompass data.DAC-997 ACUs with software version prior to 3.24 must be operated in GYRO TYPE 0 when connected to an NMEA heading reference. In this mode, the heading display is not a direct reading of the NMEA compa
NMEA Connections 2007-06-04 00:24:00 The NMEA port allows automatic Latitude, Longitude and Heading updates from a GPS receiver or gyrocompass. For GPS input, connect the 4 wires from a GPS recever to connector J13 or J11 on the back of the DAC-97. For heading input, connect pins 1 & 2 only (RX+, RX-) to the gyrocompass. To enable the interface, select the system type 8 or a combination that include 8 is selected.The DAC-97 is available with one or two NMEA/M&C ports installed at J13 and J11. If two ports are installed, use J13 for the NMEA input. If two NMEA inputs are used (heading and GPS) use J13 for the heading input. If only one M&C or NMEA GPS functions are available and only one at a time.NMEA GPS Checkout :When a NMEA GPS receiver is connected to J13 or J11, the NMEA LED on the AUX SERIAL PORT ADAPTOR (ASPA) PC board will iluminate each time a NMEA message is received. The GLL LED will illuminate each time a GPGLL or LCGLL message is received. Observe the NMEA and GLL LED's and confirm they are flashing
Ships' Gyro Compass 2007-06-04 00:14:00 Synchro Signals is an AC voltage sinewave based signal :Step-By-Step (SBS) signals (DC voltage based signal)DC voltage output changes (ON/OFF) in a specific pattern of six discrete states per degree of ships heading change. All phases high, or low, at any instant in time are illegal states (violation of gyro truth table).NMEAH heading signal(ASCII text DATA in RS-422 differential data signaling standard)Input is connected to an Aux Serial Port Adapter on the rear of the DAC-97 and the software on that ASPA board will only accept one updates every 0.75 seconds (gyro output may be more frequent). Read more:Compass
Eliminating Gyro Errors 2007-06-03 21:29:00 In Many cases, a corrupt or non existent ship's gyro compass input can couse tracking errors that are large enough to couse satellite signal losses. A gyro diagnostic mode is now available in xx96 and xx97. Pedestal Control Unit version 1.32 and higher that will uncouple the gyro reference from the azimuth rate sensor control loop. In this mode any change in ships gyro reading will not directly affect the azimuth control loop. The Pedestal Control Unit will stabilize the antenna based entirely on the azimuth rate sensor loop and the tracking information from Step Track or Conscan. To keep the azimuth rate sensor position from eventually drifting away at a rate faster than the tracking loop can correct, the tracking errors are used to regulate the rate sensor bias in a newly developed, proprietary control algorithm. We are calling this tracking error feedback Satellite reference Mode since it uses the satellite signal tracking errors as teh long term reference for the azimuth rate sen Read more:Errors
Components of Stabilization 2007-06-07 21:19:00 These are 5 of Stabilizator components :Level Cage Stepper MotorServo Amp/Motor ControllersBLDC Motors (Torque Motors)Azimuth EncoderHome SwitchLevel Cage Stepper Motor consists of :Transistors in PCU step windings (current flow) in sequence of discrete steps. These are S1, S3, S2 & S4 for full step mode or S1, S1+S3, S3, S2+S3, S2, S2+S4, S4, S4+S1 in half step mode. In each case the sequence is repeated to continue rotation.When observing voltage, a winding will be high 5 steps and low 3 steps.Continuity of each “S” winding is about 36 ohms (S1-S2 or S3-S4 would be 72 ohms).Servo Amp/Motor Controllers consists of :Commutates the Brush-Less DC motor.Controls the torque output of the BLDC motorInput from PCU 2.50VDC (NOM) for no motor drive. As voltage increases the motor shaft will be driven one direction. Decreasing voltage below 2.5VDC will drive the motor shaft the opposite direction.Outputs A,B & C to the BLDC motorHall sensor feedback from the BLDC motorBLDC Motors (Torqu Read more:Components
, Stabilization
Level Platform Installation and bias correction 2007-06-07 20:49:00 Level Platform
Replacement Procedure :Loosen the 4 Level Platform Motor mounting screws and move the motor toward the level cage to slacken the drive belt.loosen the 2 screws that retain the 15 pin harness connector to the top level platform assembly and remove the connectorremove the hex nut on the end of the level platform spindle and remove the level cage (the gold colored box).Place the drive belt over the pulley on the new level cage and assemble onto the spindle. Attach the belt to drive motor, pull the motor back to remove the slack in the belt and tighten then retaining nut.Replace the hex nut and tighten the nut until the endplay is just reduce to zero. Do not over-tighten the retaining nut.Replace the 15 pin harness connector and tighten the 2 retaining screws.Turn the antenna on and let it initialize. Place a bubble level on the top of the level platform. If the platform is level within 1 to 2 degrees, no level trim adjustment is required. If the platform is off level by mo Read more:Installation
, correction
Antenna Stabilization 2007-06-06 20:45:00 Pointing and Targeting the antenna is accurately pointing the antenna to an angular position in 3-dimensional free space. Controlled by the ACU :Antenna
DriveSatellite targetingPositional Display Antenna Drive consists of :AZ stepping, slewing and targetingEL stepping, slewing and targetingPositionnal Display consists of :Azimuth DisplayRelative DisplayElevation DisplayACU & PCU Functions associated with Pointing and targeting the antenna :Antenna Control Unit - Master, controls the antenna through the PCUPedestal Control Unit (PCU)Antenna Control Unit - Master, controls the antenna through the PCU consists of :Interface with Ships Gyro CompassInterface for GPS inputControls Pointing and Targeting of the antennaPedestal Control Unit (PCU) takes pointing and tracking direction from the ACU.3-Axis Stabilization
:Antenna Initialization - Every time the antenna is energized (or commanded to re-initialize) the PCU initializes the antenna in the following phases. Each phase must complete p
Installation Photos 2007-06-11 19:45:00 Dome Antenna lifting 1Dome Antenna lifting 2Dome Antenna lifting 3Dome Antenna lifting 4Dome Antenna lifting 5Steady on place Read more:Installation
Installation 2007-06-10 21:36:00 The Installation
Steps :Location Site Survey.Above Deck installation.Wiring.Below Deck Installation.Above deck equipment.Normal System Operation. Special operation functions.Location Site Survey :Check for blockage.Check for sources of other RF interference.Above Deck installation :Assemble base frame. Locktite and torque all hardware.Assemble lower half of the radome. Start all hardware. Silicon one flange, Locktite and tighten all hardware. Repeat for remaining flanges.Assemble upper half of the radome.Start all hardware. Silicon one flange, Locktite and tighten all hardware. Repeat for remaining flanges.Assemble reflector assembly (dish, feed and struts).Attach lower radome half to base frame.Start all hardware. Silicon one flange, Locktite and tighten all hardware. Lift antenna pedestal into lower radome half.Locktite and tighten all hardware.Lift and attach reflector and RF equipment.Lift upper radome half on lower half.Start all hardware. Silicon one flange, Locktite and t
Antenna Tracking 2007-06-10 21:25:00 Antenna Tracking
(Tracking of the satellite) - Fine adjustments to the pointing of the antenna to optimize the received signal level (AGC is monitored by the ACU). Tracking is controlled by the ACU.AGCThe internal tuner provides a DC voltage output that is directly proportional to the level of the satellite signal input. The receiver output will be positive going (voltage increases as satellite signal level increases) between 0.00-5.00 VDC. This output is converted from the analog voltage to a digital value be a 4096 bit A/D converter on the DAC-97 Main PCB. 30-40 digital counts of AGC is approximately 1dB of satellite signal. Satellite IF signal is provided into the internal tuner of the DAC-97 using the BNC or “F” connectors mounted in the rear panel.Receiver selection and tuning is set by pressing SAT key 4 times to the RCVR menu. The input is selected by pressing the NSEW key until the appropriate input is selected. Selections are Ext AGC (external connection to the Te Read more:Antenna
Stabilization Loops 2007-06-10 21:02:00 Stabilization Loops
:Azimuth Servo LoopLevel Servo LoopCross-Level Servo LoopAzimuth Servo LoopLevel Servo LoopCross-Level Servo LoopAntenna balance :Reduces the load on the motorsResponsible for 75% of the stability of the antennaTop/bottom balancingFront/rear balancingLeft/Right balancing Read more:Stabilization
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